The practice of removing snow from road surfaces and parking lots dates back many years, and is an ever increasing necessity today, as the number of miles of road increases. Snowplow equipment generally consists of the following six main components.
1. A blade to push snow to the side of the roadway or path. The blade usually has a wear bar bolted to its lower horizontal edge.
2. A table weldment to which the blade is attached.
3. An A-frame weldment to which the table is rotatably attached.
4. Linear actuators to rotate the table with respect to the A-frame, thus providing an automatic reversing assembly.
5. A means to attach the A-frame to the front of a motor vehicle.
6. A lift bar attached to the front of the motor vehicle to lift the snowplow assembly for transport.
The reversing assembly allows an operator to have the plow oriented in a straight position, discharge left position or discharge right position. In the straight position the plow blade is generally perpendicular to the direction of travel of the motor vehicle when viewed from above the vehicle. The straight position is also referred to as the bulldoze position. In the discharge left and discharge right positions, the plow blade is angled to the left or right, respectively, so as to move the snow to the left or right of the motor vehicle when the vehicle is moving in a forward direction.
In the typical arrangement, when the snowplow is lifted into a transport position for travel, the snowplow will tend to list to the side that it is angled. The problem is inherent in the geometry of the plow assembly. The center of gravity of the plow assembly moves towards the side of the vehicle to which the plow assembly is angled and causes the plow to drop to that side. Accordingly, the efficiency and the safety of the snowplowing assembly is negatively impacted. The negative effects include, but are not limited to the following.
1. The plow can list so far as to cause contact with the road surface and thereby damage the road surface or the plow.
2. The listing can also place the lower edge in the way of obstructions and cause the plow to “catch” on the obstructions causing damage to the plow and danger to the driver of the vehicle.
3. Most of these assemblies are carried with a chain or a cable that is slidably attached to the lift bar in such a way as to prevent efficient “reversing” of the plow while it is being carried in the transport position. Reversal in transport position causes significant stress to the chain or cable and the plow is subject to choppy and erratic movement. Consequently, the operator must set the plow down on the road surface to reverse it before raising the plow again for transport.
4. Listing of the plow to one side inherently causes the other side of the plow to rise. If the listing is severe, the plow can obstruct the driver's view.
5. Without a leveling device to hold the plow level, an operator can not carry the plow an inch or so off the ground while plowing in “soft conditions.”
Level lift systems exist; however, these level lift systems suffer from the following significant drawbacks.
1. The entire mechanism, excluding the lift chains, resides under the table and A-frame, putting it close to the road surface and subject to snow and ice buildup, which causes failure of the mechanism.
2. The mechanism includes two sliding chain hookups attached to or part of the front member of the table. The sliding mechanism is subject to binding if not properly and frequently lubricated and maintained. Binding causes failure to the mechanism.
3. Maintenance of the unit is difficult because the mechanism is located underneath the table.
4. The mechanism only works with a fixed length lift bar and cannot be simply adjusted to work with different lengths. Accordingly, in order to adjust the level, the lift arm must have some mode of adjustment.
Other level lift systems incorporate a single lift chain fixed at one end to the lift and at the other end to a framework welded to the table. Although this design allows the plow to settle into a level position under ideal conditions, it fails to secure the plow in a stable level position when debris builds up on either end of the plow.